My guess is they simply recognize that it’s going to take some time due to the creativity they’re having to contend with and that Arizona and Colorado aren’t going to move without having a full picture of both options. There’s nothing the Big 12 can do to force Arizona and Colorado to jump ship as they know the offer will still be there a year from now. Likewise, it doesn’t appear the B1G is imminently going to add Oregon or Washington.
That does give them time in that context. It doesn’t remove the huge cloud hanging over them though.